1. Eliminate blunders.
2. Become proficient at finding offensive and defensive tactics.
3. Stop playing “hope chess”. Analyze at least 4 ply deep, and make sure that your move improves your position and does not lead to #1 & 2 above.
4. Be aware of your opponents tactical and positional threats.
5. Become proficient in basic endgames (king and pawn and rook endgames in particular).
6. Learn the basic positional themes.
7. Work on improving your thought process.
8. Create a basic opening repertoire that fits your style of play, and does not rely on too much theory.
9. Play stronger opponents and review your games afterwards.
10. Play over annotated master games.